This invention relates to starters for internal combustion engines, and more particularly to the overhang type starters in which the pinion is positioned in front of (i.e., to the outside of) the bearing for rotatably supporting the pinion driving shaft carrying the pinion.
The overhang type starters for internal combustion engines are particularly liable to develop rust on the bearing rotatably supporting the pinion driving shaft. In order to make clear the reason therefore, let us first desribe the organization of such a starter, referring to FIG. 1 of the drawings.
FIG. 1 shows the structure of the portion around the bearing of such a starter in an axial cross section. In FIG. 1, an output shaft 1 is coupled via a planetary reduction gear device 2 to the rotational shaft 3 of the armature of the starter electric motor (not shown); on the rear outer circumferential surface of the output shaft 1 are formed helical splines 1a to which an overrunning clutch 4 is engaged at its inner surface, to be slidable in the axial direction. A pinion driving shaft 5, formed of a hardened quenched steel and disposed slidably on the output shaft 1, carries a pinion 6 formed integrally therewith at its front end. The overruning clutch 4 and the pinion driving shaft 5 with its pinion 6 constitute the pinion assembly supported axially slidably on the output shaft 1. A ball bearing 7, made of a case hardened steel, comprises: an annular inner race 7a in slidable contact with the pinion driving shaft 5; an annular outer race secured to a front bracket 8 of the starter; and a plurality of balls 7c rolling therebetween; thus, the bearing 7 supports rotatably and axially slidably the pinion driving shaft 5. Further, a pair of metallic sleeves 9 are disposed between the output shaft 1 and the pinion driving shaft 5 so as to allow rotational and axial sliding movements of the pinion driving shaft 5 with respect to the output shaft 1. A stopper 10 is secured to the front end portion of the output shaft 1 via a ring 11 to limit the forward (toward right in the figure) movement of the pinion 6 by abutting on the stepped portion 5aof the pinion driving shaft 5 formed on its interior side surface. An electromagnetic switch 12 shifts the pinion assembly via a lever 13, which is pivoted at its middle and is coupled at its upper end to the armature or plunger 14 of the electromagnetic switch 12 and at its lower end to the rear side of the overrunning clutch 4.
The operation of the starter of FIG. 1 is as follows. When an electric current is supplied to the electromagnetic switch 12 from a storage battery, etc., the plunger 1 is attracted by the resulting magnetic force toward left in the figure; thus, the lever 13 rotates counterclockwise to drive and shift forward the overrunning clutch 4 and the pinion driving shaft 5, so that the pinion 6 is brought into engagement with the ring gear (not shown) of the engine. Further, due to the action of the electromagnetic switch 12, the starter motor is supplied with an energization current to develop a torque; the resulting rotation of the motor is transmitted via the planetary reduction gear device 2 to the output shaft 1, and further, to the pinion driving shaft 5 via the overrunning clutch 4; thus, the resulting rotation of the pinion 6 starts the engine.
As point out first, the above type of starters suffer from the development of rust on the bearing. Namely, when water containg mud or salt is splashed upon the starter, as often happens in the case of the starter attached, for example, to an automotive engine or an outboard engine of a small boat, this corrosive water enters from the front opening to the interior portion at which the bearing 7 is located. This eventually results in the development of rust on the bearing 7. As a result, the smooth sliding contact between the inner race of the bearing 7 and the pinion driving shaft 5 is impaired.